Low power consumption, and thus long battery life, is critical to the success of next-generation ad-hoc wireless devices. With this in mind, many ad-hoc networks allow nodes to periodically sleep, or power down, in order to conserve battery life. The period of activity and inactivity is usually referred to as a node's duty cycle (DC).
With the above in mind, it would be beneficial to allow devices to keep their radios off for a majority of the time, yet be aware of the presence and information services being beaconed by neighboring devices. If a radio is off for too long of a time, it may miss information being broadcast by other nodes, however, if a radio is on for long periods of time, it may needlessly listen during periods of inactivity.
When all devices are in the same administrative domain (e.g. same owner or a shared, well-known configuration) with precisely maintained clocks, it is trivial to arrange the nodes' duty cycles to maximize battery life. However, there are many cases where the collection of nodes to be synchronized is not within the same administrative domain. For example, laptop computers and other mobile devices co-resident inside a coffee house while their individual owners make a purchase.
It would thus be beneficial for all nodes, even those without a shared administrative domain, to be synchronized such that they all transmit within a same period of time, so that an efficient duty cycle can be achieved. Therefore, a need exists for a method and apparatus for synchronizing nodes within a communication system that allows nodes to transmit and receive information during a synchronized time period.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Those skilled in the art will further recognize that references to specific implementation embodiments such as “circuitry” may equally be accomplished via replacement with software instruction executions either on general purpose computing apparatus (e.g., CPU) or specialized processing apparatus (e.g., DSP). It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.